U.S. patent application number 09/988236 was filed with the patent office on 2003-07-03 for two-part polyurethane adhesives for structural finger joints and method therefor.
Invention is credited to Chen, Gang-Fung, Walworth, Gary J..
Application Number | 20030125449 09/988236 |
Document ID | / |
Family ID | 25533956 |
Filed Date | 2003-07-03 |
United States Patent
Application |
20030125449 |
Kind Code |
A1 |
Chen, Gang-Fung ; et
al. |
July 3, 2003 |
Two-part polyurethane adhesives for structural finger joints and
method therefor
Abstract
One aspect of the present invention is an adhesive composition
formed from two packs. One pack includes an isocyanate-functional
prepolymer formed by reacting a polyisocyanate with an alcohol
(e.g., polyol). The isocyanate equivalents from the polyisocyanate
exceed the hydroxyl equivalents from the alcohol. The second pack
is an aqueous polymer emulsion. These two packs are combined to
form the novel adhesive composition. Another aspect of the
invention is a method for joining together two surfaces of wood
products by application of an adhesive thereto. The first step in
this method is to mist with water the wood product surfaces to be
joined. An adhesive composition then is applied to the misted wood
product surfaces. Alternatively, the water misting can be replaced
with an aqueous emulsion being part of the adhesive composition.
Finally, the adhesive composition is cured.
Inventors: |
Chen, Gang-Fung; (Dublin,
OH) ; Walworth, Gary J.; (Dublin, OH) |
Correspondence
Address: |
Jerry K. Mueller, Jr.
Mueller and Smith, LPA
7700 Rivers Edge Drive
Columbus
OH
43235
US
|
Family ID: |
25533956 |
Appl. No.: |
09/988236 |
Filed: |
November 19, 2001 |
Current U.S.
Class: |
524/501 ;
156/295; 156/307.3; 156/310; 156/314; 156/331.2; 428/407; 428/413;
428/423.1; 428/425.1; 428/520; 524/507; 524/555; 524/591; 524/813;
525/123; 525/127; 528/44 |
Current CPC
Class: |
Y10T 428/2991 20150115;
C08G 18/10 20130101; C08L 2666/04 20130101; Y10T 428/31591
20150401; B32B 27/12 20130101; Y10T 428/31511 20150401; B32B 21/14
20130101; Y10T 428/2998 20150115; Y10T 428/31551 20150401; Y10T
428/31928 20150401; C09J 175/04 20130101; C08G 18/10 20130101; C08G
18/302 20130101; C09J 175/04 20130101; C08L 2666/04 20130101 |
Class at
Publication: |
524/501 ;
524/507; 524/813; 524/591; 524/555; 525/127; 525/123; 528/44;
428/425.1; 428/423.1; 428/407; 428/413; 428/520; 156/307.3;
156/295; 156/310; 156/314; 156/331.2 |
International
Class: |
C08K 003/20 |
Claims
1. An adhesive composition, which comprises: (a) an
isocyanate-functional prepolymer formed by reacting a
polyisocyanate with an alcohol, where the isocyanate equivalents
from the polyisocyanate exceeds the hydroxyl equivalents from the
alcohol; and (b) an aqueous polymer emulsion.
2. The adhesive composition of claim 1, wherein said alcohol is
selected from one or more of acrylates, esters, vinyls, castor
oils, or polymers, containing active alcohol groups.
3. The adhesive composition of claim 2, wherein said alcohol is
selected from one or more of aliphatic and aromatic polyether
polyols optionally alkylated, or caprolactone-based polyols.
4. The adhesive composition of claim 3, wherein said active
hydrogen group component is a block polyethylene or polypropylene
oxide homo- or co-polymer ranging in molecular weight from about
300 to about 3,000.
5. The adhesive composition of claim 1, wherein said
isocyanate-terminated prepolymer is made from an isocyanate
component selected from hexamethylene diisocyanate, toluene
diisocyanate (TDI), diphenylmethane diisocyanate (MDI), m- and
p-phenylene diisocyanates, bitolylene diisocyanate, cyclohexane
diisocyanate (CHDI), bis-(isocyanatomethyl) cyclohexane
(H.sub.6XDI), dicyclohexylmethane diisocyanate (H.sub.12MDI), dimer
acid diisocyanate (DDI), trimethyl hexamethylene diisocyanate,
lysine diisocyanate and its methyl ester, isophorone diisocyanate,
methyl cyclohexane diisocyanate, 1,5-napthalene diisocyanate,
xylylene and xylene diisocyanate and methyl derivatives thereof,
polymethylene polyphenyl isocyanates,
chlorophenylene-2,4-diisocyanate, polyphenylene diisocyanates,
isophorone diisocyanate (IPDI), hydrogenated methylene diphenyl
isocyanate (HMDI), tetramethyl xylene diisocyanate (TMXDI),
hexamethylene diisocyanate (HDI), or oligomers thereof, and
mixtures thereof.
6. The adhesive composition of claim 1, wherein said isocyanate
prepolymer contains a defoamer and an inhibitor.
7. The adhesive composition of claim 1, wherein the weight ratio of
said isocyanate-functional prepolymer to said aqueous polymer
emulsion ranges from about 95/5 to about 60/40.
8. The adhesive composition of claim 7, wherein the weight ratio of
said isocyanate-functional prepolymer to said aqueous polymer
emulsion ranges from about 90/10 to about 70/30.
9. The adhesive composition of claim 1, wherein said aqueous
polymer emulsion is one or more of acrylic emulsions, vinyl
emulsions, styrene-butadiene polymeric emulsion latices, polyvinyl
alcohol emulsions, polyurethane dispersions, polyvinyl
acetate-ethylene copolymer emulsions, or carboxylated acrylic
latexes.
10. The adhesive composition of claim 9, wherein said aqueous
polymer emulsion is heat curable or radio frequency curable.
11. A laminated wood product adhesively joined with the cured
residue of an adhesive, which comprises: (a) an
isocyanate-functional prepolymer formed by reacting a
polyisocyanate with an alcohol, where the isocyanate equivalents
from the polyisocyanate exceeds the hydroxyl equivalents from the
alcohol; and (b) an aqueous polymer emulsion., the weight ratio of
(a) to (b) ranging from about 95/5 to about 60/40.
12. The laminated wood product of claim 11, wherein said adhesive
has been cured by heat or radio frequency (RF) curing.
13. The laminated wood product of claim 11, wherein said alcohol is
selected from one or more of acrylates, esters, vinyls, castor
oils, or polymers, containing active alcohol groups.
14. The laminated wood product of claim 13, wherein said alcohol is
selected from one or more of aliphatic and aromatic polyether
polyols optionally alkylated, or caprolactone-based polyols.
15. The laminated wood product of claim 14, wherein said alcohol is
a block polyethylene or polypropylene oxide homo- or co-polymer
ranging in molecular weight from about 300 to about 3,000.
16. The laminated wood product of claim 11, wherein said
isocyanate-terminated prepolymer is made from an isocyanate
component selected from hexamethylene diisocyanate, toluene
diisocyanate (TDI), diphenylmethane diisocyanate (MDI), m- and
p-phenylene diisocyanates, bitolylene diisocyanate, cyclohexane
diisocyanate (CHDI), bis-(isocyanatomethyl) cyclohexane
(H.sub.6XDI), dicyclohexylmethane diisocyanate (H.sub.12MDI), dimer
acid diisocyanate (DDI), trimethyl hexamethylene diisocyanate,
lysine diisocyanate and its methyl ester, isophorone diisocyanate,
methyl cyclohexane diisocyanate, 1,5-napthalene diisocyanate,
xylylene and xylene diisocyanate and methyl derivatives thereof,
polymethylene polyphenyl isocyanates, chlorophenylene-2,4-diisoc-
yanate, polyphenylene diisocyanates, isophorone diisocyanate
(IPDI), hydrogenated methylene diphenyl isocyanate (HMDI),
tetramethyl xylene diisocyanate (TMXDI), hexamethylene diisocyanate
(HDI), or oligomers thereof, and mixtures thereof.
17. The laminated wood product of claim 11, wherein said isocyanate
prepolymer contains a defoamer and an inhibitor.
18. The laminated wood product of claim 11, wherein the weight
ratio of said isocyanate-functional prepolymer to said aqueous
polymer emulsion ranges from about 90/10 to about 70/30.
19. The laminated wood product of claim 11, wherein said aqueous
polymer emulsion is one or more of acrylic emulsions, vinyl
emulsions, styrene-butadiene polymeric emulsion latices, polyvinyl
alcohol emulsions, polyurethane dispersions, polyvinyl
acetate-ethylene copolymer emulsions, or carboxylated acrylic
latexes.
20. The laminated wood product of claim 11, wherein the wood to be
joined has a moisture content of less than about 10% by weight.
21. Method for joining together two surfaces of wood products
having a moisture content of less than about 10% by weight by
application of an aqueous adhesive thereto, which comprises the
steps of: (a) misting the wood product surfaces to be joined with
water; (b) applying to said aqueous adhesive composition to said
misted wood product surfaces; and (c) curing said adhesive
composition.
22. The method of claim 21, wherein said aqueous adhesive
composition is applied to said misted wood product surfaces within
about 5 minutes after said misting.
23. The method of claim 21, wherein said surfaces are misted to
saturation.
24. The method of claim 21, wherein said adhesive composition
comprises: (a) an isocyanate-functional prepolymer formed by
reacting a polyisocyanate with an alcohol, where the isocyanate
equivalents from the polyisocyanate exceeds the hydroxyl
equivalents from the alcohol; and (b) an aqueous polymer emulsion.,
the weight ratio of (a) to (b) ranging from about 95/5 to about
60/40.
25. The method of claim 21, wherein said adhesive has been cured by
heat or radio frequency (RF) curing.
26. The method of claim 24, wherein said alcohol is selected from
one or more of acrylates, esters, vinyls, castor oils, or polymers,
containing active alcohol groups.
27. The method of claim 26, wherein said alcohol is selected from
one or more of aliphatic and aromatic polyether polyols optionally
alkylated, or caprolactone-based polyols.
28. The method of claim 27, wherein said alcohol is a block
polyethylene or polypropylene oxide homo- or co-polymer ranging in
molecular weight from about 300 to about 3,000.
29. The method of claim 24, wherein said isocyanate-terminated
prepolymer is made from an isocyanate component selected from
hexamethylene diisocyanate, toluene diisocyanate (TDI),
diphenylmethane diisocyanate (MDI), m- and p-phenylene
diisocyanates, bitolylene diisocyanate, cyclohexane diisocyanate
(CHDI), bis-(isocyanatomethyl) cyclohexane (H.sub.6XDI),
dicyclohexylmethane diisocyanate (H.sub.12MDI), dimer acid
diisocyanate (DDI), trimethyl hexamethylene diisocyanate, lysine
diisocyanate and its methyl ester, isophorone diisocyanate, methyl
cyclohexane diisocyanate, 1,5-napthalene diisocyanate, xylylene and
xylene diisocyanate and methyl derivatives thereof, polymethylene
polyphenyl isocyanates, chlorophenylene-2,4-diisocyanate,
polyphenylene diisocyanates, isophorone diisocyanate (IPDI),
hydrogenated methylene diphenyl isocyanate (HMDI), tetramethyl
xylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), or
oligomers thereof, and mixtures thereof.
30. The method of claim 24, wherein said isocyanate prepolymer
contains a defoamer and an inhibitor.
31. The method of claim 24, wherein the weight ratio of said
isocyanate-functional prepolymer to said aqueous polymer emulsion
ranges from about 90/10 to about 70/30.
32. The method of claim 24, wherein said aqueous polymer emulsion
is one or more of acrylic emulsions, vinyl emulsions,
styrene-butadiene polymeric emulsion latices, polyvinyl alcohol
emulsions, polyurethane dispersions, polyvinyl acetate-ethylene
copolymer emulsions, or carboxylated acrylic latexes.
33. A method for adhesively joining wood product surfaces, which
comprises: (1) providing an adhesive composition comprising: (a) an
isocyanate-functional prepolymer formed by reacting a
polyisocyanate with an alcohol, where the isocyanate equivalents
from the polyisocyanate exceeds the hydroxyl equivalents from the
alcohol; and (b) an aqueous polymer emulsion. (2) applying to said
aqueous adhesive composition to said wood product surfaces; and (3)
curing said adhesive composition,
34. The adhesive composition of claim 33, wherein said alcohol is
selected from one or more of acrylates, esters, vinyls, castor
oils, or polymers, containing active alcohol groups.
35. The adhesive composition of claim 34, wherein said alcohol is
selected from one or more of aliphatic and aromatic polyether
polyols optionally alkylated, or caprolactone-based polyols.
36. The adhesive composition of claim 35, wherein said active
hydrogen group component is a block polyethylene or polypropylene
oxide homo- or co-polymer ranging in molecular weight from about
300 to about 3,000.
37. The adhesive composition of claim 33, wherein said
isocyanate-terminated prepolymer is made from an isocyanate
component selected from hexamethylene diisocyanate, toluene
diisocyanate (TDI), diphenylmethane diisocyanate (MDI), m- and
p-phenylene diisocyanates, bitolylene diisocyanate, cyclohexane
diisocyanate (CHDI), bis-(isocyanatomethyl) cyclohexane
(H.sub.6XDI), dicyclohexylmethane diisocyanate (H.sub.12MDI), dimer
acid diisocyanate (DDI), trimethyl hexamethylene diisocyanate,
lysine diisocyanate and its methyl ester, isophorone diisocyanate,
methyl cyclohexane diisocyanate, 1,5-napthalene diisocyanate,
xylylene and xylene diisocyanate and methyl derivatives thereof,
polymethylene polyphenyl isocyanates, chlorophenylene-2,4-diisoc-
yanate, polyphenylene diisocyanates, isophorone diisocyanate
(IPDI), hydrogenated methylene diphenyl isocyanate (HMDI),
tetramethyl xylene diisocyanate (TMXDI), hexamethylene diisocyanate
(HDI), or oligomers thereof, and mixtures thereof.
38. The adhesive composition of claim 33, wherein said isocyanate
prepolymer contains a defoamer and an inhibitor.
39. The adhesive composition of claim 33, wherein the weight ratio
of said isocyanate-functional prepolymer to said aqueous polymer
emulsion ranges from about 95/5 to about 60/40.
40. The adhesive composition of claim 39, wherein the weight ratio
of said isocyanate-functional prepolymer to said aqueous polymer
emulsion ranges from about 90/10 to about 70/30.
41. The adhesive composition of claim 33, wherein said aqueous
polymer emulsion is one or more of acrylic emulsions, vinyl
emulsions, styrene-butadiene polymeric emulsion latices, polyvinyl
alcohol emulsion s, polyurethane dispersions, polyvinyl
acetate-ethylene copolymer emulsions, or carboxylated acrylic
latexes.
42. The adhesive composition of claim 41, wherein said curing is by
heat curing or radio frequency curing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] None
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] The present invention generally relates to adhesives for
joining wood products, and more particularly to two-part
polyurethane adhesives modified with an aqueous emulsion.
[0004] Glued wood products have been traditionally used in this
country in a variety of applications. The adhesives for such bonded
or laminated wood products conventionally are based on
phenol-formaldehyde, urea-formaldehyde, polyvinyl acetate,
resorcinol-formaldehyde, polymeric diphenylmethane diisocyanate
(MDI), and hot met adhesives. The glued wood products include
plywood, particleboard, oriented strand board (OSB), medium density
fiberboard (MDF), laminated veneer lumber (LVL), laminated beams,
and a variety of other engineered wood products. Among them,
laminated beams, I-beams, LVL, and a variety of engineered wood
products are used for structural wood applications. Generally,
these engineered wood products require an initial finger jointing
of short pieces of wood or parallel laminated veneers (PLV) before
they can be constructed into long and/or thick beams or lumbers and
in the case of I-Beams an adhesive is required to assemble the
I-Beam itself. A fast curing structural adhesive is required to
manufacture I-Beams in both the web-to-flange joint as well as the
butt joint between web pieces. Consequently, it is important that,
in the finger-jointed area and the I-Beam bonding areas, the
adhesive have good strength, structural adhesive properties, and
cure quickly. For present purposes, all of the foregoing products
are known as "laminated wood products."
[0005] At present, phenol-resorcinol-formaldehyde (PRF) is widely
used in industry for finger joint applications. When adhesive is
applied to the fingers, the finger jointed wood or PLV is crowded
together using an end pressure until a "tip gap" of 1-40 mils is
achieved. Its is essential that the fingers do not "bottom out."
The finger joints then are moved into a curing zone where hot
platens or dielectric plates are used to cure the finger joints
under heat or radio frequency and pressure for typically less than
30 seconds and then the joints are removed away from the curing
zone. The adhesives must be able to fill the gaps or voids between
the fingers when curing is complete in order for the product to
exhibit good strength and a smooth appearance.
[0006] One the other hand, the speed of curing must be fast under
these conditions in order to hold the finger-jointed pieces
together for further processing, such as beam lamination and
I-joint assembly. This is especially true in a high-speed
commercial finger jointing process. Generally, adhesives with high
solids and fast curing profiles are regarded as appropriate for
such an application.
[0007] It should be mentioned also that two-part PRF and
melamine-formaldehyde (MF) adhesives generally are used in industry
as adhesives in preparation of radio frequency (RF) cured finger
joint assemblies. Both of these adhesives are highly polar, which
makes them respond well to RF curing. RF curing drives the bondline
temperature sufficiently high to permit the MF or PRF to condense
quickly. Due to the rigid ring structure of both PRF and MF, these
adhesives cure to give a high T.sub.g, rigid, three-dimensional
network in a short time; thus, producing acceptable immediate
handling strength (proof-loading).
[0008] Heretofore, U.S. Pat. No. 3,931,088 proposes an aqueous
adhesive composition of an aqueous solution of polyvinyl alcohol,
an aqueous emulsion of vinyl acetate polymer or an aqueous latex of
a butadiene polymer in combination with a hydrophobic solution of
an isocyanate compound. RE No. 34,093 proposes an aqueous adhesive
composed of an aqueous emulsion of a polymer or interpolymer of one
or more of vinyl monomers in combination with an aqueous emulsion
of a polyisocyanate, which has been at least partially reacted with
a C.sub.6 to C.sub.30 alkanol.
BRIEF SUMMARY OF THE INVENTION
[0009] One aspect of the present invention is an adhesive
composition formed from two packs. One pack includes an
isocyanate-functional prepolymer formed by reacting a
polyisocyanate with an alcohol. The isocyanate equivalents from the
polyisocyanate exceed the hydroxyl equivalents from the alcohol.
The second pack is an aqueous polymer emulsion. These two packs are
combined to form the novel adhesive composition. "Alcohol" for
present purposes includes polyols.
[0010] Another aspect of the invention is a method for joining
together two surfaces of wood products by application of an
adhesive thereto. The first step in this method is to mist with
water the wood product surfaces to be joined. An adhesive
composition then is applied to the misted wood product surfaces.
Alternatively, the water misting can be replaced with an aqueous
emulsion being part of the adhesive composition. Finally, the
adhesive composition is cured. This method works best when the
moisture content (MC) of the wood products to be joined is less
than about 10%.
[0011] Advantages of the present invention include the ability of
the inventive adhesive to qualify as a structural adhesive. Another
advantage is the ability of the inventive adhesive to qualify as an
exterior structural adhesive for engineered wood applications.
These and other advantage will be readily apparent to those skilled
in the art based on the disclosure set forth herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a fuller understanding of the nature and advantages of
the present invention, reference should be had to the following
detailed description taken in connection with the accompanying
drawings, in which:
[0013] FIG. 1 graphically plots the percent wood failure as a
function of the time between water misting the wood surfaces and
the application of the adhesive composition in a vacuum-pressure
test, as reported in Example 5;
[0014] FIG. 2 graphically plots the percent wood failure as a
function of the time between water misting the wood surfaces and
the application of the adhesive composition in a two-cycle boil
test, as reported in Example 5;
[0015] FIG. 3 graphically plots the percent wood failure as a
function of moisture content of the wood, where the adhesive
compositions were applied 3 minutes after misting and 23 minutes
after misting in a vacuum-pressure test, as reported in Example 6;
and
[0016] FIG. 4 graphically plots the percent wood failure as a
function of moisture content of the wood, where the adhesive
compositions were applied 3 minutes after misting and 23 minutes
after misting in a two-cycle boil test, as reported in Example
6.
[0017] The drawings will be described in further detail below.
DETAILED DESCRIPTION OF THE INVENTION
[0018] It is well known that woods are porous materials that
contain different moisture contents, depending upon type of wood,
storage environment, etc. Moisture contents can vary from as low as
5 wt-% to greater than 30 wt-%. For adhesives to properly bond
wood, it is important that the adhesive penetrates deep into the
wood and interlock with the cellulose structure upon cross-linking.
In order to achieve this, the invention relies of wood with a lower
moisture content, say less than about 10% MC, with the addition of
water just before application of the adhesive composition. The
"dry" wood sucks up the water and presumably creates a "vacuum",
which sucks in the coating composition.
[0019] One method for achieving this result is to employ an aqueous
component in the adhesive composition. To strike a balance, then,
an isocyanate-terminated prepolymer becomes the predominant
component of the adhesive composition and an aqueous polymer
emulsion a minor component. Such a composition would supply water
that would penetrate into the interior of the wood, thus creating a
"vacuum" that would pull the adhesive polymers down into the
interior of the wood for greater bonding strength. Water also would
react with the prepolymer for cure of the prepolymer in addition to
any, if at all, reaction between the prepolymer and the aqueous
polymeric component. Such a balanced cure results in strong bonds
by virtue of the wood penetration of the adhesive coupled with the
necessary speed of cure required in commercial settings. The
examples will amply demonstrate the performance of the inventive
adhesive in engineered wood applications.
[0020] Isocyanate-functional prepolymers are made from
polyisocyanates reacted with a compound containing active hydrogen
functionality with hydroxyl groups being typical, although
mercaptan groups, amine groups, and carboxyl groups also can be
used. Polyisocyanates are conventional in nature and include, for
example, hexamethylene diisocyanate, toluene diisocyanate (TDI),
diphenylmethane diisocyanate (MDI), m- and p-phenylene
diisocyanates, bitolylene diisocyanate, cyclohexane diisocyanate
(CHDI), bis-(isocyanatomethyl) cyclohexane (H.sub.6XDI),
dicyclohexylmethane diisocyanate (H.sub.12MDI), dimer acid
diisocyanate (DDI), trimethyl hexamethylene diisocyanate, lysine
diisocyanate and its methyl ester, isophorone diisocyanate, methyl
cyclohexane diisocyanate, 1,5-napthalene diisocyanate, xylylene and
xylene diisocyanate and methyl derivatives thereof, polymethylene
polyphenyl isocyanates, chlorophenylene-2,4-diisocyanate,
polyphenylene diisocyanates available commercially as, for example,
Mondur MR or Mondur MRS, isophorone diisocyanate (IPDI),
hydrogenated methylene diphenyl isocyanate (HMDI), tetramethyl
xylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), or
oligomer materials of these materials such as a trimer of IPDI, HDI
or a biuret of HDI, and the like and mixtures thereof.
Triisocyanates and high-functional isocyanates also are well known
and can be used to advantage. Aromatic and aliphatic diisocyanates,
for example, (including biuret and isocyanurate derivatives) often
are available as pre-formed commercial packages and can be used to
advantage in the present invention.
[0021] Preferred polyols for reacting with the polyisocyanates
include, for example, polyether polyols (e.g., block polyethylene
and polypropylene oxide homo- and co-polymers ranging in molecular
weight from about 300 to about 3,000) optionally alkylated (e.g.,
polytetramethylene ether glycols), caprolactone-based polyols, and
the like. However, the component also may be formulated with
mixtures of aliphatic and aromatic polyols, or a multi-functional,
active hydrogen-bearing polymer. Thus, in addition to polyether
polyols, the hydroxyl-functional component may include derivatives
of acrylates, esters, vinyls, castor oils, as well as polymers and
mixtures thereof.
[0022] Isocyanate equivalents should predominate over active
hydrogen equivalents in the polyisocyanate/polyol reaction mixture
in order for the resulting prepolymer to contain residual
isocyanate groups. Reaction conditions for this reaction are well
known in the art, such as described by Heiss, et al., "Influence of
Acids and Bases on Preparation of Urethane Polymers", Industrial
and Engineering Chemistry, Vol. 51, No. 8, August 1959, pp.
929-934. Depending upon the reaction conditions used (such as, for
example, temperature and the presence of strong acids or bases, and
catalysts), the reaction may lead to the formation of ureas,
allophanates, biurets, or isocyanates.
[0023] Virtually any aqueous emulsion polymer system can be used in
connection with the inventive adhesive. Representative emulsion
polymer systems include, inter alia, acrylic and vinyl emulsions,
styrene-butadiene polymeric emulsion latices, polyvinyl alcohol
emulsions, polyurethane dispersions, polyvinyl acetate-ethylene
copolymer emulsions, carboxylated acrylic latexes, and any other
type of polymer emulsions.
[0024] The major component of the inventive adhesive composition is
the isocyanate prepolymer. The predominant cure mechanism, then,
involves moisture cure of the isocyanate prepolymer from water
misting the surfaces to be joined, water in the wood products to be
joined, and water in the aqueous emulsion component of the system.
It should be recognized, however, that active hydrogen groups
contained in the aqueous emulsion, other than water, also can react
with free isocyanate groups in the isocyanate prepolymer. Thus, the
ratio of isocyanate prepolymer to aqueous emulsion will determine
the structural property of the cured adhesive. Without the presence
of aqueous emulsion, the isocyanate prepolymer acts as a moisture
curable adhesive and ultimately will form a tough, highly
crosslinked structure. With the presence of excess aqueous
emulsion, the isocyanate prepolymer will be consumed by the excess
amount of water to form low molecular weight polyamine, which will
decrease the crosslink density. Therefore, the mix ratio of
isocyanate prepolymer to aqueous emulsion should be selected in
such a way that the active hydrogen groups in the aqueous emulsion
also will participate in the crosslinking reaction. Consequently,
the mix ratio of isocyanate prepolymer and aqueous emulsion can
range from about 95/5 to 60/40. Preferably, the mix ratio can range
from about 90/10 to 70/30.
[0025] Also, the isocyanate prepolymer must be separated from the
aqueous emulsion in order to preclude premature gellation and
crosslinking. This is because the isocyanate group from the
prepolymer can react with either water in the emulsion polymer at a
relatively fast rate of reaction, particularly under the influence
of catalysis using, for example, dibutyl tin dilaurate catalyst
(T-12 brand, see Examples). Thus, the inventive wood adhesive is a
two-pack or two-part composition whose packs or parts are mixed
together just prior to application to the wood.
[0026] Application of the inventive glue is conventional for this
art. Cure of the glue can be by simple heating as taught in this
art and practiced commercially at, say, from about room temperature
to about 175.degree. C. for times ranging from as short as say, 30
seconds, on up to about 2 minutes, with cure times dependent upon
reaction temperature and catalyst concentration. The adhesive can
be made to cure under the influence of radio frequency or microwave
by incorporating polar ingredients, such as, for example, aluminum
chloride, sodium chloride, or other suitable ingredients known by
those skilled in the art.
[0027] While the invention has been described with reference to a
preferred embodiment, those skilled in the art will understand that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope of the invention.
In addition, many modifications may be made to adapt a particular
situation or material to the teachings of the invention without
departing from the essential scope thereof. Therefore, it is
intended that the invention not be limited to the particular
embodiment disclosed as the best mode contemplated for carrying out
this invention, but that the invention will include all embodiments
falling within the scope of the appended claims. In this
application all units are in the metric system and all amounts and
percentages are by weight, unless otherwise expressly indicated.
Also, all citations referred herein are expressly incorporated
herein by reference.
EXAMPLES
Example 1
Preparation of PUP1 With Talc (5815-049)
[0028] A polyether diol (462.6 g, MW of 2,000, Ashland code
033-192, Ashland Chemical, Dublin, Ohio) was charged into a 2-liter
three-neck round bottom reaction flask and heated to 100.degree. C.
Talc (488.6 g) was added slowly to the reaction flask with
continuous mechanical agitation. When the Talc addition was
complete, a vacuum was applied (1.5-2.0 cm Hg) for 30 minutes to
reduce the moisture content of the reaction flask contents to
<0.01% by weight.
[0029] The reaction mixture then was allowed to cool to 85.degree.
C. before a polymeric methylene diisocyanate or MDI (677.4 g,
Mondur MRS poly(methylenephenylene) polyisocyanate, average
functionality of 2.8, average equivalent weight of 133, NCO content
of 31.6%, viscosity@25.degree. C. of 250 cps, Miles Chemical) was
added to the reaction flask. The reaction was allowed to proceed at
75.degree. c for 3 hours. Dibutyl tin dilaurate (1.63 g, DABCO.RTM.
T-1 2 catalyst, 18.0% total tin, Air Products and Chemicals, Inc.,
Allentown, Pa.) and a D-1400 defoamer (1.63 g, polydimethylsiloxane
and treated amorphous silica foam control agent, Dow Corning
Corporation, Midland, Mich.) were added when the reaction mixture
was cooled to 50.degree. C. The product was unloaded from the
reaction flask after an additional 30 minutes of agitation.
Example 2
Preparation of PUP2 Without Talc (6680-34)
[0030] A polyether diol (590.75 g, MW of 2,000, Ashland code
033-192, Ashland Chemical, Dublin, Ohio), Mondur MRS polyisocyanate
(994.0 g), and D-1400 defoamer (1.60 g) were charged into a 2-liter
three-neck round bottom reaction flask held under constant
mechanical agitation and a nitrogen blanket at ambient temperature.
T-12 catalyst (1.62 g) was added to the reaction mixture and a mild
exotherm was observed. A second aliquot of T-12 catalyst (1.6 g)
was added approximately 30 to 40 minutes later with a peak exotherm
of 40.degree.-45.degree. C. observed. The reaction was permitted to
proceed for an additional one hour at which time
monophenyl-dichlorophosphate (4.0 g) was added to the reaction
mixture with an additional 10 minutes of agitation before the
product was unloaded from the reaction flask.
Example 3
Preparation of Aqueous Emulsion Polymer
[0031] Various commercially available aqueous emulsion polymers
were evaluated. These included consumer and commercial paint,
latex, and emulsion shown below:
[0032] 1. Rhoplex TR-520 is an acrylic-based anionic emulsion from
Rohm and Haas, T.sub.g=6.degree. C., NV (non-volatile solids)=51%,
pH=3, and Brookfield viscosity at 25.degree.C. of <100 cps.
[0033] 2. Rhoplex N-619 is an acrylic-based anionic emulsion from
Rohm and Haas, T.sub.g=28.degree. C., NV=57%, pH=7.8, and
Brookfield viscosity at 25.degree. C. of 50-200 cps.
[0034] 3. Arolon.RTM. 870-W-51 is a styrene butadiene emulsion from
Reichhold, T.sub.g=2.degree. C., NV=51%, pH=8-9, and Brookfield
viscosity at 25.degree. C. of <500 cps.
[0035] 4. Aquathane.RTM. AD 97950-00 is an aqueous dispersion of
polyurethane ionomer from Reichhold, MP=105-115 C, NV=44-46%,
pH=6.5-8.5, and Brookfield viscosity at 25.degree. C. of <1000
cps.
[0036] 5. Carbobond.TM. 26373 is an acrylic polymer emulsion from
BF Goodrich, Nev.=56-59%, pH=3.2-4.2, and Brookfield viscosity at
25.degree. C. of <1000 cps.
[0037] 6. Hycar.RTM. 26091 is a carboxylated acrylic latex from B F
Goodrich, T.sub.g=20.degree. C., NV=50%, pH=6.8 with Brookfield
viscosity at 25.degree. C. of 35 cps.
[0038] 7. Airflex.RTM. 7200 is a polyvinyl acetate-ethylene
copolymer emulsion from Air Products Company, T.sub.g=0.degree. C.,
NV=73%, pH=4.0-5.5, and Brookfield viscosity at 25.degree. C. of
1500-3000 cps.
[0039] 8. Vinac XX-21 0 is a polyvinyl acetate homopolymer from Air
Products Company, T.sub.g=35.degree. C., NV=55%, pH=4.5-6.0, and
Brookfield viscosity at 25.degree. C. of 1000-1400 cps.
[0040] 9. Vinac XX-230 is a polyvinyl acetate homopolymer from Air
Products Company, T.sub.g=35.degree. C., NV=55%, pH=4.56.0, and
with Brookfield viscosity at 25.degree. C. of 2000-2600 cps.
[0041] 10. Vinac XX-240 is a polyvinyl acetate homopolymer from Air
Products Company, T.sub.g=35.degree. C., NV=55%, pH=4.56.0, and ith
Brookfield viscosity at 25.degree. C. of 2900-3700 cps.
[0042] 11. ISOSET.RTM. 1000 is a self-crosslinking polyvinyl
acetate copolymer from Ashland Chemical, T.sub.g=5.degree. C.,
NV=47-49%, pH=2.5-4.0, and Brookfield viscosity at 25.degree. C. of
4000-6000 cps.
[0043] 12. Flat acrylic house paint is a consumer paint
manufactured by The Valspar Corporation (CAS No. 7732-18-5; acrylic
copolymer latex containing TiO.sub.2, ethylene glycol, Talc, and
silica).
[0044] 13. TB-II is a consumer wood glue, a polyvinyl acetate
emulsion adhesive from Franklin International.
[0045] 14. Flat wall paint is a consumer paint manufactured by
Sherwin Williams (part number: W36 A 750; a vinyl polymer latex,
with fillers, water, and ethylene glycol).
[0046] 15. Wood exterior primer is a consumer wood primer
manufactured by Sherwin Williams (part number W45 702 O/M; tall oil
alkyd polymer containing fillers and TiO.sub.2 in mineral
spirits).
Example 4
Adhesive Performance With and Without Water Misting
[0047] ASTM D-5751 testing was undertaken using high density
(specific gravity, sp. gr., 0.57 to 0.59 g/cm.sup.3) Douglas fir
using PUP1 of Example 1. The following results were recorded:
1 TABLE 1* Water Dry Vacuum-Pressure 2-Cycle Boil MC % Misting PSI
Wf % PSI Wf % PSI Wf % 10.8 No 2,164 65 616 3 193 (8) (136) (3)
(105) 10.5 Yes 2,122 85 917 29 599 29 (59) (4) (58) (7) 7.6 No
1,852 10 583 2 132 3 (12( (3) (170) (4) 7.1 Yes 2,408 70 868 41 531
55 (105) (11) (168) (16) *MC is moisture content Wf % is % Wood
Failure Numbers in parentheses are standard deviation
[0048] These results demonstrate that misting of the wood results
in a much higher rate of wood failure and consequent improvement in
adhesive performance, especially with low moisture content
wood.
[0049] The results of ASTM D-2559 delamination tests on Douglas fir
for the same PUP1 based adhesive are set forth below:
2TABLE 2 Weight Spec. Water Increase Ratio Delamination Gravity MC
% Misting (3 blocks) Final Cycle (%) 0.525 10.6 No 1.27 1.27 1.39
4.2 0.529 10.6 Yes 1.26 1.25 1.33 2.1 0.524 7.5 No 1.33 1.26 1.37
19.4 0.531 7.4 Yes 1.31 1.25 1.29 3.1
[0050] Again, it can be seen that at low a moisture content (MC) of
7.5%, water misting plays a critical factor in the final outcome of
delamination percentage. With misting, the final cycle delamination
percentage is 3.1% as compared to 19.4% when no misting is
employed.
Example 5
Time Study of Adhesive Performance with Misting
[0051] Vacuum-Pressure and Two-Cycle Boil ASTM D-5751 tests were
undertaken at different times of adhesive application following
misting of the wood. The amount of water misted was determined to
be approximately 2 grams per 5".times.12" board. The results
recorded are set forth below and in FIGS. 1 (vacuum-pressure) and 2
(boil).
3TABLE 3 ASTM D-5751 Vacuum-Pressure Tests Douglas Fir (Sp. Gr. =
0.57-0.58, MC = 6-8%), Closed Assembly Time = 6-8 minutes Time of
adhesive Vacuum-Pressure application after Dry (average of 7
specimens) water misting Strength Wood Failure Strength Wood
Failure (min) (psi) (%) (psi) (%) 0 1,776 95 824 .+-. 110 60 .+-.
16 5 1,749 90 815 .+-. 77 50 .+-. 19 10 1,658 50 643 .+-. 132 30
.+-. 15 15 1,605 60 665 .+-. 182 26 .+-. 7 20 1,461 40 638 .+-. 115
29 .+-. 6 40 1,208 10 559 .+-. 171 18 .+-. 12
[0052]
4TABLE 4 ASTM D-5751 Two-cycle Boil Tests Douglas Fir (Sp. Gr. =
0.57-0.58, MC = 6-8%), Closed Assembly Time = 6-8 minutes Time of
adhesive Two-cycle Boil Tests application after Dry (average of 7
specimens) water misting Strength Wood Failure Strength Wood
Failure (min) (psi) (%) (psi) (%) 0 1,776 95 550 .+-. 110 61 .+-. 7
5 1,749 90 591 .+-. 140 46 .+-. 11 10 1,658 50 529 .+-. 169 36 .+-.
8 15 1,605 60 500 .+-. 276 26 .+-. 17 20 1,461 40 495 .+-. 203 29
.+-. 7 40 1,208 10 333 .+-. 144 14 .+-. 8
[0053] These tests reveal that gluing immediately after water
misting produced the best results, as the adhesive passed the ASTM
D-5751 test despite use of high density Douglas fir (Sp.
Gr.=0.57-0.58) used. Every minute thereafter results in decreased
wood failure percentages. One explanation of this phenomenon comes
from established information that a Douglas fir panel having
5".times.12" dimension absorbs approximately 400 g of water when
totally saturated with water. The amount of water misted was
approximately 2 g, which is far less than the amount of water
absorbed at saturation. Consequently, most of the misted water is
expected to penetrate deeply into the wood. Experimental testing
determined that, after 20 minutes of standing at room temperature,
the water misted wood (5".times.12" panel) lost 10% of its absorbed
water. Presumably this loss of water was due to evaporation from
the wood surface. Therefore, it is possible that, when the wood
surface is still somewhat wet (1 minute after misting), the applied
adhesive prevents water from evaporating from the wood panel. The
continued penetration of water into the wood presumably creates low
pressure (vacuum condition) to induce adhesive penetration and,
thus, a high wood failure is seen in Tables 3 and 4. When adhesive
is applied 10 to 20 minutes after water misting, most of the water
has already penetrated into the wood. This translates into little
vacuum being created. Thus, a low wood failure is seen in Tables 3
and 4. This may explain the unsatisfactory results obtained for
those samples having the adhesive applied at a longer time after
water misting.
Example 6
Time Study of Adhesive Performance with Misting
[0054] In this study, adhesive PUP1 was applied to woods of
different moisture content 3 minutes after water misting and 23
minutes after water misting. This experiment was based on a simple
factorial design to see if the "vacuum" condition induces adhesion
penetration to cause high wood failure. Again, Vacuum-Pressure and
Two-Cycle Boil ASTM D-5751 tests were undertaken with the following
results. These results also are illustrated in FIG. 3 (line 10 for
3 min and line 12 for 23 min) for vacuum-pressure and in FIG. 4
(line 14 for 3 min and line 16 for 23 min) for boil tests.
5TABLE 5 Vacuum-Pressure Tests Douglas Fir (Sp. Gr. = 0.54-0.56,
CAT = 6-8 minutes) Time of Wood failure adhesive Strength (psi) (%)
application (average of 7 (average of 7 Test No. MC % of wood (min)
specimens) specimens) 1 <5 3 917 .+-. 82 60 .+-. 18 2 <5 23
918 .+-. 52 49 .+-. 18 3 10-11 3 934 .+-. 51 51 .+-. 13 4 10-11 23
783 .+-. 64 32 .+-. 18 5 >30 3 792 .+-. 74 18 .+-. 10 6 >30
23 827 .+-. 113 14 .+-. 8
[0055]
6TABLE 6 Two-Cycle Boil Tests Douglas Fir (Sp. Gr. = 0.54-0.56, CAT
= 6-8 minutes) Time of Wood failure adhesive Strength (psi) (%)
application (average of 7 (average of 7 Test No. MC % of wood (min)
specimens) specimens) 1 <5 3 740 .+-. 117 69 .+-. 19 2 <5 23
635 .+-. 243 58 .+-. 28 3 10-11 3 712 .+-. 70 63 .+-. 8 4 10-11 23
399 .+-. 101 27 .+-. 10 5 >30 3 431 .+-. 122 19 .+-. 6 6 >30
23 200 .+-. 106 15 .+-. 8
[0056] These results strongly support a possible mechanism of
action of water misting. It can be seen from Tables 5 and 6 that
adhesive performance (as measured by % wood failure) decreases as
the wood moisture content increases for those adhesives applied 3
minutes after water misting. Similar results also were obtained
with those adhesive applied 23 minutes after water misting. As wood
moisture content increases, the "vacuum" condition created by water
misting is not as strong as for wood with low wood moisture
content. The mechanism, then, may be that the water mist penetrates
into the dry wood causing a "vacuum", which induces the adhesive's
penetration into the wood with consequent improvement in
performance (higher wood failure).
Example 7
Preparation of Two-Part Polyurethane Adhesives
[0057] Various two-part polyurethane adhesive were prepared by
mixing PUP2 of Example 2 with the aqueous emulsion polymers (AEP)
of Example 3. The pot-lives of The various adhesives ranged from
about 2 to 30 minutes, depending on the mix ratio, catalyst
selected, and catalyst's concentration. Generally, as the PUP2
concentration in the mix increased, so did the pot life of the
mixture. The required cure times of the adhesives ranged from 30
minutes to 4 hours, depending on the temperature. Data displayed in
Table 7, below, are based on a PUP2:AEP weight ratio of 4:1 with
cure at 330.degree. F. for 30 seconds for laminated veneer lumber
(LVL). Tests were taken 30 minutes and 24 hours after the cured LVL
finger joints stood at room temperature following cure.
7TABLE 7 Description 30 Minutes 24 Hours Flat Wall paint 3,207 .+-.
865 19 .+-. 14 8,417 .+-. 1618 77 .+-. 13 Flat acrylic 2,403 .+-.
940 10 .+-. 11 7,752 .+-. 965 80 .+-. 26 house paint Wood exterior
496 .+-. 102 4 .+-. 3 7,521 .+-. 936 65 .+-. 10 primer Arlon 870
17,83 .+-. 156 10 .+-. 4 8,083 .+-. 307 87 .+-. 6 Airflex 7200 953
.+-. 454 4 .+-. 3 6,846 .+-. 637 88 .+-. 3 Aquathane 4,434 .+-. 598
43 .+-. 19 6,591 .+-. 679 88 .+-. 3 AD 97950-00 Carbobond 26373
1,232 .+-. 365 4 .+-. 5 5,239 .+-. 144 80 .+-. 17 Hycar 26091 5,334
.+-. 1073 68 .+-. 25 8,659 .+-. 1513 90 .+-. 5 Emulsion Rhoplex
N-619 449 .+-. 388 1 .+-. 3 3,255 .+-. 184 12 .+-. 3 Rhoplex TR-520
2,301 .+-. 365 9 .+-. 3 7,585 .+-. 1238 85 .+-. 9 TB-II 3,750 .+-.
861 33 .+-. 9 8,805 .+-. 1813 95 .+-. 5
[0058] The above-tabulated data demonstrates excellent initial bond
strength with bond strength continuing to increase over time.
Example 8
Finger Joint Strength Development
[0059] In order to demonstrate strength development of the
inventive adhesive formulation, PUP2 was admixed with Vinac XX-230
(Air Products Company) at a 4:1 weight ratio and applied to black
spruce finger joints (2".times.4"), cured at ambient temperature,
and tension tested at different times thereafter. The results
recorded are set forth below.
8TABLE 8 STRENGTH WOOD FAILURE SAMPLE CURE TIME (psi) (%) 1 30 min
1,752 0 2 45 min 2,038 0 3 45 min 2,514 0 4 60 min 4,610 0 5 24 hrs
8,810 100 6 24 hrs 9,048 100
[0060] These test results again demonstrate good initial bond
strengths that develop into outstanding bond strengths at 24 hours
(almost 9,000 psi).
Example 9
Finger Joint Strength Development
[0061] In order to demonstrate strength development at different
catalyst (T-12 brand dibutyl tin dilaurate) concentrations, PUP2
was added with higher T-12 concentrations and mixed with ISOSET
1000 at a 4:1 weight ratio. The mixed adhesives were applied to
black spruce pine finger joints (2".times.4"), cured at ambient
temperature, and tension tested at different times following
application and cure. The results recorded are set forth in Table
9
9TABLE 9 T-12 CONCENTRATION CURE TIME STRENGTH WOOD FAILURE (%)
(min) (psi) (%) 0.2 30 1,010 0 45 2,076 0 45 1,771 0 60 3,010 0 24
hrs 7,448 100 24 hrs 9,219 100 0.4 30 1,790 0 30 1,518 0 45 3,048 0
45 2,648 0 0.6 30 1,295 0 30 2,819 0 45 4,229 10 45 5,410 15
[0062] Similarly, PUP2 (containing 0.6% of T-12) was mixed with
Vinac XX-210 at 80/20 volume ratio and applied to black spruce pine
finger joints (2".times.4"). The ambient temperature cured strength
development (tension test) are shown below.
10 TABLE 10 CURE TIME STRENGTH WOOD FAILURE Sample ID (min) (psi)
(%) 1 15 1,067 0 2 30 2,286 0 3 45 3,790 0 4 60 5,029 25 5 120
7,586 45
[0063] These results demonstrate that when PUP2 contained greater
than about 0.4% T-12, the finger joints exhibited strengths of
greater than 2,880 psi after 45 minutes, which is the strength
required for the proof-load in a typical finger joint commercial
line of manufacture.
Example 10
ASTM D-5751 Results
[0064] In order to adjudge whether the inventive adhesives can
qualify for structural property engineered wood applications, PUP2
of Example 2 was mixed with AEP from Example 3 at 90/10 and 80/20
mix ratios and applied to different wood species for ASTM D-5751
testing. The following results were recorded.
11 TABLE 11 Dry Vacuum-pressure Two-cycle Boil Strength Wood
failure Strength Wood failure Strength Wood failure Sample ID No.*
(psi) (%) (psi) (%) (psi) (%) C6079-165A 1,884 .+-. 163 99 .+-. 2
1,030 .+-. 68 64 .+-. 19 817 .+-. 77 65 .+-. 27 C6079-172A 1,456
.+-. 404 83 .+-. 16 932 .+-. 103 51 .+-. 23 743 .+-. 90 59 .+-. 32
C6079-172B 1,479 .+-. 152 73 .+-. 19 1,070 .+-. 25 71 .+-. 15 683
.+-. 82 51 .+-. 15 C6079-174A 1,675 .+-. 104 71 .+-. 24 993 .+-. 77
44 .+-. 16 827 .+-. 46 46 .+-. 28 C6079-174B 1,704 .+-. 105 74 .+-.
16 1,045 .+-. 90 48 .+-. 16 752 .+-. 72 45 .+-. 16 C6079-174C 1,745
.+-. 66 76 .+-. 17 1,064 .+-. 74 53 .+-. 22 854 .+-. 72 50 .+-. 18
C6079-174D 1,583 .+-. 242 76 .+-. 17 1,077 .+-. 48 34 .+-. 19 704
.+-. 123 54 .+-. 17 *C6079-165A is PUP2/ISOSET 1000 at 80/20 mix
ratio applied (static mixed) to Douglas fir (Sp. Gr. = .46 MC =
10-11%) C6079-172A is PUP2/Vinac XX-210 at 90/10 mix ratio applied
(hand mixed) to Douglas fir (Sp. Gr. = 0.48, MC = 10-11%)
C6079-172B is PUP2/Vinac XX-210 at 80/20 mix ratio applied (static
mixed) to Douglas fir (Sp. Gr. = 0.48, MC = 9-10%) C6079-174B is
PUP2/ISOSET 1000 at 90/10 mix ratio applied (hand mixed) to Douglas
fir (Sp. Gr. = .48) MC = 10-11% C6079-174C is PUP2/Vinac XX-210 at
80/20 mix ratio applied (static mixed) to Douglas fir (Sp. Gr. =
.45) MC = 10-11% C6079-174D is PUP2/Vinac XX-210 at 80/20 mix ratio
applied (static mixed) to Douglas fir (Sp. Gr. = .48) MC =
10-11%
[0065] The above-tabulated ASTM D-5751 test results indicate that
the inventive adhesive system is suitable for structural
applications. Such test results include, inter alia, good dry and
wet strength, as well as good wood failure.
Example 11
ASTM D-2559 Results
[0066] In order to qualify adhesives for exterior structural
engineered wood application, one of the tests required is to have
low degrees of delamination (5% or less) in the ASTM D-2559 test.
Thus, tests were conducted on Douglas fir (sp. Gr. of 0.50,
moisture content of 12%, Table 12) and black spruce (sp. Gr. of
0.44-0.48, moisture content of 10-11%, Table 13). The following
results were recorded.
12TABLE 12 FORMULATION C-6079-161B C-6079-164B Prepolymer + 0.3%
DMDEE PUP2 -- Prepolymer -- PUP2 AEP ISOSET .RTM. 1000 ISOSET .RTM.
1000 Mix Ratio 80:20 80:20 CAT (min) Immediate Immediate OAT (min)
<1 <1 % Delamination Per Glue Line GL 1* 0.7636 0.6404 GL 2
0.1568 2.5324 GL 3 0.9904 0.3128 GL 4 0.3416 0.7544 GL 5 4.2568
0.8636 TOTAL % DELAMINATION 6.5092 5.1036 *GL is glue line
[0067]
13 TABLE 13 FORMULATION C-6079-169B Prepolymer + 0.6% T-12 PUP2 AEP
Vinac XX-210 Mix ratio 80:20 CAT (min) Immediate OAT (min) <1 GL
1* 0.1972 GL 2 0.1460 GL 3 0.1352 GL 4 0.4288 GL 5 0.6880 TOTAL %
DELAMINATION 1.5952 *GL is glue line
[0068] These test results indicate that both adhesives showed a low
degree of delamination, which is required for exterior structural
application.
* * * * *